The Doctor, Jamie, and Victoria find themselves at a refinery where a mysterious menace is trying to sabotage the refinery.
This is one of the best of the lost stories. It's suspenseful and often legitimately terrifying. It works well as an audio given the brilliant music and sound effects. The guest cast does a superb job, particularly Victor Maddern as the commanding officer losing control. The story also marks Victoria's departure from the TARDIS and does a lovely job building towards that departure and getting the audience emotionally invested. Add to that this is the first story featuring the Sonic Screwdriver and this is yet another classic story from Season Five.